1. Field of the Invention
The invention relates to for a ball grid array (BGA) device, more particularly to a testing apparatus adapted for use in testing BGA devices.
2. Description of the Related Art
Ball grid array (BGA) packages are high pin count integrated circuit packages that are widely used in surface mounting applications. Referring to FIG. 1, a known BGA device 1 includes a semiconductor device 12 disposed on a dielectric insulating substrate 11 that is formed with circuit traces (not shown) for electrical connection with the semiconductor device 12. A plurality of signal, ground and voltage source solder balls 13, 14 and 15, that are formed from tin, are provided on a bottom face of the insulating substrate 11 and are connected electrically to the circuit traces to serve as electrical contacts for the BGA device 1. The signal solder balls 13 are arranged in an array at a periphery of the bottom face. The voltage source solder balls 15 are arranged in a squarely looped array at a central portion of the bottom face. The ground solder balls 14 are arranged in rows within the squarely looped array, and are spaced apart from the voltage source solder balls 15. In the mass production of BGA devices 1, a number of insulating substrates 11 are initially interconnected as a large insulating plate. After the circuit traces are formed, the large insulating plate is subsequently cut to form the individual insulating substrates 11, thereby resulting in exposed conductive contacts (not shown) on the margins 16 of each insulating substrate 11.
Referring to FIGS. 2 and 3, a conventional testing apparatus for testing BGA devices includes a movable carrier 3 for receiving a BGA device 1, a tester 2, and a moving device (not shown) for moving the BGA device 1 from the carrier 3 to the tester 2. The carrier 3 has a squarely looped flange 31 formed on a bottom side of an inner surface of the carrier 3 for isolating the BGA device 1 from the bottom side. The squarely looped flange 31 has a cross-section larger than that of the squarely looped array of the voltage source solder balls 15. The tester 2 includes a testing circuit unit 21 provided with a testing circuit layout, and a socket 23 formed from an insulator material and retained on the testing circuit unit 21 via a mounting seat 22 that is fixed on the testing circuit unit 21. The socket 23 is formed with a receiving space 25 that opens upwardly. Guide members 26 project inwardly from the socket 23 into the receiving space 25. The socket 23 has a contactor plate 27 disposed at a bottom end of the receiving space 25 and formed with a plurality of spring probes or pogo pins 29 that are registered with the solder balls 13, 14 and 15 of the BGA device 1 that is to be tested. A surface mount matrix 24 interconnects the pogo pins 29 and the testing circuit layout on the testing circuit unit 21. The pogo pins 29, in turn, interconnect the BGA device 1 and the surface mount matrix 24.
When testing the BGA device 1 for defects, the BGA device 1 is loaded into the receiving space 25 of the socket 23 to enable the solder balls 13, 14 and 15 to contact the pogo pins 29. The guide members 26 function to align the BGA device 1 in relation to the pogo pins 29 in the receiving space 25 by contacting the margins 16 of the insulating substrate 11 so as to guide the insulating substrate 11 into the receiving space 25 in a proper position. The BGA device 1 is then pressed toward the pogo pins 29 to ensure electrical connection between the BGA device 1 and the testing circuit layout 28 on the testing circuit unit 21 via the pogo pins 29 and the surface mount matrix 5.
Some of the drawbacks of the conventional testing apparatus described beforehand are as follows:
1. As the distances of the margins 16 of the insulating substrate 11 from the solder balls 13, 14 and 15 can vary due to errors that may occur during the cutting of the insulating substrate 11, there are chances that the solder balls 13, 14 and 15 will not be placed properly on the pogo pins 29 when aligning the BGA device 1 in relation to the pogo pins 29 by referring to the margins 16 of the insulating substrate 11. When the BGA device 1 is pressed toward the pogo pins 29, scratching of the surface of the solder balls 13, 14 and 15 by the pogo pins 29 is likely occur. The solder material removed from one of the solder balls 13, 14 and 15 can get trapped between an adjacent pair of the solder balls 13, 14 and 15 and can result in short-circuiting. Moreover, the solder balls, once scratched, will decrease of the yield of non-defective products during the surface mounting of the BGA device 1.
2. As mentioned beforehand, exposed conductive contacts are present on the margins 16 of the insulating substrate 11 of the BGA device 1. After the BGA device 1 has been tested for defects and is removed from the socket 23, static electricity is usually observed between the guide members 26 in the receiving space 25 and exposed conductive contacts at the margins 16 of the BGA device 1. The static electricity is discharged via the BGA device 1 since the socket 23 is made entirely from an insulator material, and can result in damage to the BGA device 1.
3. Due to the lengths of the pogo pins 29, the BGA device 1 experiences loss during high frequency testing.